Retrieve an image from the server, store it in localStorage, and display it

Question

This should be simple enough, but after wrestling with it for hours, I still can't get it to work. So far, all my attempts have resulted in the image becoming 'corrupted or truncated', according to firefox.

Retrieve the image from the server with a jquery-ajax call:

 $.ajax({
                async: false,
                url: db[key]["DocumentLink"],
                success: function (result2) {

Base64 encode the image, and store it in localStore:
In this example I'm using the jquery base64-encoding plugin, but I've tried several.

                        var dbKey = "Doc " + db[key]["ID"] + " " + db[key]["Title"];
                        console.log("storing: " + db[key]["DocumentLink"] + " in " + dbKey + "\n");
                        localStorage.removeItem(dbKey);
                        var base64Image = $.base64Encode(result2);
                        console.log(base64Image.length);
                        localStorage.setItem(dbKey, base64Image);
                       console.log("is stored: " + db[key]["DocumentLink"] + " in " + dbKey + "\n");
                }
})

Display the image with a data url:

function openImageFromDB(dbKey) {
    console.log("Trying to display image with key " + dbKey);
    var base64Img = localStorage.getItem(dbKey);
    document.getElementById("documentHolder").src='data:image/jpeg;base64,' + base64Img;
}

The corresponding img:

 <img id="documentHolder" alt="Image view placeholder" src="" />

However, on every try, firefox displays:

Image corrupt or truncated: data:image/jpeg;base64,77+977+977+977+9a<... much longer string>

The Url: points to a valid jpeg image, and the base64Image.length and the error message show that the var / localStorage actually contain what seems to be base64 encoded data.

Any ideas?

Answer 1

• DEMO: http://so.lucafilosofi.com/retrieve-an-image-from-the-server-store-it-in-localstorage-and-display-it

Javascript (AJAX call)

function LoadImg(filename) {
    var xmlhttp;
    if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp = new XMLHttpRequest();
    } else { // code for IE6, IE5
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {     
            document.getElementById("documentHolder").src = "data:image/png;base64," + xmlhttp.responseText;
        }
    };    
    xmlhttp.open("GET", 'load.php?LoadImg='+filename );
    xmlhttp.send(null);
}

PHP ( load.php )

<?php
 if (isset($_GET['LoadImg'])) {
  header("Content-Type: image/png");
  $file = file_get_contents($_GET['LoadImg']);
  echo base64_encode($file);
}
?>

---

Read this may help you:

• Base 64 encode vs loading an image file
• How to encode image data within an HTML file?
• How can you encode a string to Base64 in JavaScript?
• Get image data in JavaScript?

PS: maybe your Base64 is wrong?